Re: [PATCH 4/5] python/qemu: qmp: Make QEMUMonitorProtocol a context manager

[John Snow <jsnow@redhat.com>]

On 12/27/19 8:41 AM, Wainer dos Santos Moschetta wrote:
> This implement the __enter__ and __exit__ functions on
> QEMUMonitorProtocol class so that it can be used on 'with'
> statement and the resources will be free up on block end:
> 
> with QEMUMonitorProtocol(socket_path) as qmp:
>     qmp.connect()
>     qmp.command('query-status')
> 
> Signed-off-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
> ---
>  python/qemu/qmp.py | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/python/qemu/qmp.py b/python/qemu/qmp.py
> index 914b8c6774..6d55f53595 100644
> --- a/python/qemu/qmp.py
> +++ b/python/qemu/qmp.py
> @@ -139,6 +139,15 @@ class QEMUMonitorProtocol:
>                  raise QMPConnectError("Error while reading from socket")
>              self.__sock.settimeout(None)
>  
> +    def __enter__(self):
> +        # Implement context manager enter function.
> +        return self
> +
> +    def __exit__(self, exc_type, exc_value, exc_traceback):
> +        # Implement context manager exit function.
> +        self.close()
> +        return False
> +
>      def connect(self, negotiate=True):
>          """
>          Connect to the QMP Monitor and perform capabilities negotiation.
> @@ -259,8 +268,10 @@ class QEMUMonitorProtocol:
>          """
>          Close the socket and socket file.
>          """
> -        self.__sock.close()
> -        self.__sockfile.close()
> +        if self.__sock:
> +            self.__sock.close()
> +        if self.__sockfile:
> +            self.__sockfile.close()

Not evident on cold read: does self.close() change self.__sock and
self.__sockfile such that they are false-ish?

close() I suspect might need to actually unset the __sock and __sockfile
fields.

>  
>      def settimeout(self, timeout):
>          """
>